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Tag Archives: nano titanium dioxide

Thanks to Lynn L. Bergeson’s Sept. 21, 2016 posting for information about the US Environmental Protection Agency’s (EPA) research into what happens to the nanoparticles when your nanosunscreen washes off into a swimming pool. Bergeson’s post points to an Aug. 15, 2016 EPA blog posting by Susanna Blair,

… It’s not surprising that sunscreens are detected in pool water (after all, some is bound to wash off when we take a dip), but certain sunscreens have also been widely detected in our ecosystems and in our wastewater. So how is our sunscreen ending up in our environment and what are the impacts?

Blair goes on to provide a good brief description of nanosunscreens before moving onto her main topic,

Many sunscreens contain titanium dioxide (TiO2) because it absorbs UV radiation, preventing it from damaging our skin. But titanium dioxide decomposes into other molecules when in the presence of water and UV radiation. This is important because one of the new molecules produced is called a singlet oxygen reactive oxygen species. These reactive oxygen species have been shown to cause extensive cell damage and even cell death in plants and animals. To shield skin from reactive oxygen species, titanium dioxide engineered nanomaterials are often coated with other materials such as aluminum hydroxide (Al(OH)3).

EPA researchers are testing to see whether swimming pool water degrades the aluminum hydroxide coating, and if the extent of this degradation is enough to allow the production of potentially harmful reactive oxygen species. In this study, the coated titanium dioxide engineered nanomaterials were exposed to pool water for time intervals ranging from 45 minutes to 14 days, followed by imaging using an electron microscope. Results show that after 3 days, pool water caused the aluminum hydroxide coating to degrade, which can reduce the coating’s protective properties and increase the potential toxicity. To be clear, even with degraded coating, the toxicity measured from the coated titanium dioxide, was significantly less [emphasis mine] than the uncoated material. So in the short-term – in the amount of time one might wear sunscreen before bathing and washing it off — these sunscreens still provide life-saving protection against UV radiation. However, the sunscreen chemicals will remain in the environment considerably longer, and continue to degrade as they are exposed to other things.

…

Blair finishes by explaining that research is continuing as the EPA researches the whole life cycle of engineered nanomaterials.

Lynn L. Bergeson has a July 21, 2016 post on Nanotechnology Now with information about a July 14, 2016 European Commission (EC) regulation allowing nanoscale titanium dioxide to be used as a UV (ultraviolet) filter, i.e., sunscreen in various cosmetic and beauty products. You can find more details about the regulation and where it can be found in Bergeson’s posting. I was most interested in the specifics about the nano titanium dioxide particles,

… Titanium dioxide (nano) is not to be used in applications that may lead to exposure of the end user’s lungs by inhalation. Only nanomaterials having the following characteristics are allowed:
– Purity ¡Ý [sic] 99 percent;
– Rutile form, or rutile with up to 5 percent anatase, with crystalline structure and physical appearance as clusters of spherical, needle, or lanceolate shapes;
– Median particle size based on number size distribution ¡Ý [sic] 30 nanometers (nm);
– Aspect ratio from 1 to 4.5, and volume specific surface area ¡Ü [sic] 460 square meters per cubic meter (m2/cm3);
– Coated with silica, hydrated silica, alumina, aluminum hydroxide, aluminum stearate, stearic acid, trimethoxycaprylylsilane, glycerin, dimethicone, hydrogen dimethicone, or simethicone;
– Photocatalytic activity ¡Ü [sic] 10 percent compared to corresponding non-coated or non-doped reference, and
– Nanoparticles are photostable in the final formulation.

I’m guessing that purity should be greater than 99%, that median particle size should be greater than 30 nm, that aspect ratio should be less than 460 square meters per cubic meter, and that photocatalytic activity should be less than 10%.

If anyone should know better or have access to the data, please do let me know in the comments section.

Because they are lawyers, I was intrigued by a Nov. 4, 2015 article on managing nanotechnology risks by Michael Lisak and James Mizgala of Sidley Austin LLP for Industry Week. I was also intrigued by the language (Note: A link has been removed),

The inclusion of nanotechnologies within manufacturing processes and products has increased exponentially over the past decade. Fortune recently noted that nanotechnology touches almost all Fortune 500 companies and that the industry’s $20 billion worldwide size is expected to double over the next decade. [emphasis mine]

Yet, potential safety issues have been raised and regulatory uncertainties persist. As such, proactive manufacturers seeking to protect their employees, consumers, the environment and their businesses – while continuing to develop, manufacture and market their products – may face difficult choices in how to best navigate this challenging and fluid landscape, while avoiding potential “nanotort,” [emphasis mine] whistleblower, consumer fraud and regulatory enforcement lawsuits. Doing so requires forward-thinking advice based upon detailed analyses of each manufacturer’s products and conduct in the context of rapidly evolving scientific, regulatory and legal developments.

I wonder how many terms lawyers are going to coin in addition to “nanotort”?

The lawyers focus largely on two types of nanoparticles, carbon nanotubes, with a special emphasis on multi-walled carbon nantubes (MWCNT) and nano titanium dioxide,

Despite this scientific uncertainty, international organizations, such as the International Agency for Research on Cancer [a World Health Organization agency], have already concluded that nano titanium dioxide in its powder form and multi-walled carbon nanotube-7 (“MWCNT-7”) [emphasis mine] are “possibly carcinogenic to humans.” As such, California’s Department of Public Health lists titanium dioxide and MWCNT-7 as “ingredients known or suspected to cause cancer, birth defects, or other reproductive toxicity as determined by the authoritative scientific bodies.” Considering that processed (i.e., non-powdered) titanium dioxide is found in products like toothpaste, shampoo, chewing gum and candies, it is not surprising that some have focused upon such statements.

There’s a lot of poison in the world, for example, apples contain seeds which have arsenic in them and, for another, peanuts can be carcinogenic and they can also kill you, as they are poison to people who are allergic to them.

On the occasion of Dunkin’ Donuts removing nano titanium dioxide as an ingredient in the powdered sugar used to coat donuts, I wrote a March 13, 2015 posting, where I quote extensively from Dr. Andrew Maynard’s (then director of the University of Michigan Risk Science Center now director of the Risk Innovation Lab at Arizona State University) 2020 science blog posting about nano titanium dioxide and Dunkin’ Donuts,

He describes some of the research on nano titanium dioxide (Note: Links have been removed),

… In 2004 the European Food Safety Agency carried out a comprehensive safety review of the material. After considering the available evidence on the same materials that are currently being used in products like Dunkin’ Donuts, the review panel concluded that there no evidence for safety concerns.

Most research on titanium dioxide nanoparticles has been carried out on ones that are inhaled, not ones we eat. Yet nanoparticles in the gut are a very different proposition to those that are breathed in.

Studies into the impacts of ingested nanoparticles are still in their infancy, and more research is definitely needed. Early indications are that the gastrointestinal tract is pretty good at handling small quantities of these fine particles. This stands to reason given the naturally occurring nanoparticles we inadvertently eat every day, from charred foods and soil residue on veggies and salad, to more esoteric products such as clay-baked potatoes. There’s even evidence that nanoparticles occur naturally inside the gastrointestinal tract.

You can find Andrew’s entire discussion in his March 12, 2015 post on the 2020 Science blog. Andrew had written earlier in a July 12, 2014 posting about something he terms ‘nano donut math’ as reported by As You Sow, the activist group that made a Dunkin’ Donuts shareholder proposal which resulted in the company’s decision to stop using nano titanium dioxide in the powdered sugar found on their donuts. In any event, Andrew made this point,

In other words, if a Dunkin’ Donut Powdered Cake Donut contained 8.9 mg of TiO2 particles smaller than 10 nm, it would have to have been doused with over 1 million tons of sugar coating! (Note update at the end of this piece)

Clearly something’s wrong here – either Dunkin’ Donuts are not using food grade TiO2 but a nanopowder with particle so small they would be no use whatsoever in the sugar coating (as well as being incredibly expensive, and not FDA approved). Or there’s something rather wrong with the analysis!

If it’s the latter – and it’s hard to imagine any other plausible reason for the data – it looks like As You Sow ended up using rather dubious figures to back up their stakeholder resolution. I’d certainly be interested in more information on the procedures Analytical Sciences used and the checks and balances they had in place, especially as there are a number of things that can mess up a particle analysis like this.

…

Update July 14: My bad, I made a slight error in the size distribution calculation first time round. This has been corrected in the article above. Originally, I cited the estimated Mass Median Diameter (MMD) of the TiO2 particles as 167 nm, and the Geometric Standard Deviation (GSD) as 1.6. Correcting an error in the Excel spreadsheet used to calculate the distribution (these things happen!) led to a revised estimate of MMD = 168 nm and a GSD of 1.44. These may look like subtle differences, but when calculating the estimated particle mass below 10 nm, they make a massive difference. With the revised figures, you’d expect less than one trillionth of a percent of the mass of the TiO2 powder to be below 10 nm!! (the original estimate was a tenth of a millionth of a percent). In other words – pretty much nothing! The full analysis can be found here.

Update November 16 2014. Based on this post, As You Sow checked the data from Analytical Sciences LLC and revised the report accordingly. This is noted above.

It would seem that if there are concerns over nano titanium dioxide in food, the biggest would not be the amounts ingested by consumers but inhalation by workers should they breathe in large quantities when they are handling the material.

As for the MWCNTs, they have long raised alarms but most especially the long MWCNTs and for people handling them during the course of their work day. Any MWCNTs found in sports equipment and other consumer products are bound in the material and don’t pose any danger of being inhaled into the lungs, unless they should be released from their bound state (e.g. fire might release them).

After some searching for MWCNT-7, I found something which seems also to be known as Mitsui MWCNT-7 or Mitsui 7-MWCNT (here’s one of my sources). As best I understand it, Mitsui is a company that produces an MWCNT which they have coined an MWCNT-7 and which has been used in nanotoxicity testing. As best I can tell, MWCNT is MWCNT-7.

The lawyers (Lisak and Mizgala) note things have changed for manufacturers since the early days and they make some suggestions,

…

One thing is certain – gone are the days when “sophisticated” manufacturers incorporating nanotechnologies within their products can reasonably expect to shield themselves by pointing to scientific and regulatory uncertainties, especially given the amount of money they are spending on research and development, as well as sales and marketing efforts.

First, manufacturers should fully understand the life-cycle of nanomaterials within their organization. For some, nanomaterials may be an explicit focus of innovation and production, making it easier to pinpoint where nanotechnology fits into their processes and products. For others, nanomaterials may exist either higher-up or in the back-end of their products’ supply chain. …

Second, manufacturers should understand and stay current with the scientific state-of-the-art as well as regulatory requirements and developments potentially applicable to their employees, consumers and the environment. An important consideration related to efforts to understand the state-of-the-art is whether or not manufacturers should themselves expend resources to advance “the science” in seeking to help find answers to some of the aforementioned uncertainties. …

The lawyers go on to suggest that manufacturers should consider proactively researching nanotoxicity so as to better defend themselves against any future legal suits.

Encouraging companies to proactive with toxicity issues is in line with what seems to be an international (Europe & US) regulatory movement putting more onus on producers and manufacturers to take responsibility for safety testing. (This was communicated to me in a conversation I had with an official at the European Union Joint Research Centre where he mentioned REACH regulations and the new emphasis in response to my mention of similar FDA (US Food and Drug Administration) regulations. (We were at the 2014 9th World Congress on Alternatives to Animal Testing in Prague, Czech republic.)

For anyone interested in the International Agency for Research on Cancer you can find it here.

It’s been a busy few days for titanium dioxide, nano and otherwise, as the news about its removal from powdered sugar in Dunkin’ Donuts products ripples through the nano blogosphere. A March 6, 2015 news item on Azonano kicks off the discussion with an announcement,

Dunkin’ Brands, the parent company of the Dunkin’ Donuts chain, has agreed to remove titanium dioxide, a whitening agent that is commonly a source of nanomaterials, from all powdered sugar used to make the company’s donuts. As a result of this progress, the advocacy group As You Sow has withdrawn a shareholder proposal asking Dunkin’ to assess and reduce the risks of using nanomaterials in its food products.

Returning to the ‘debate’, a July 11, 2014 article by Sarah Shemkus for a sponsored section in the UK’s Guardian newspaper highlights an initiative taken by an environmental organization, As You Sow, concerning titanium dioxide in Dunkin’ Donuts’ products (Note: A link has been removed),

The activists at environmental nonprofit As You Sow want you to take another look at your breakfast doughnut. The organization recently filed a shareholder resolution asking Dunkin’ Brands, the parent company of Dunkin’ Donuts, to identify products that may contain nanomaterials and to prepare a report assessing the risks of using these substances in foods.

Their resolution received a fair amount of support: at the company’s annual general meeting in May, 18.7% of shareholders, representing $547m in investment, voted for it. Danielle Fugere, As You Sow’s president, claims that it was the first such resolution to ever receive a vote. Though it did not pass, she says that she is encouraged by the support it received.

“That’s a substantial number of votes in favor, especially for a first-time resolution,” she says.

The measure was driven by recent testing sponsored by As You Sow, which found nanoparticles of titanium dioxide in the powdered sugar that coats some of the donut chain’s products. [emphasis mine] An additive widely used to boost whiteness in products from toothpaste to plastic, microscopic titanium dioxide has not been conclusively proven unsafe for human consumption. Then again, As You Sow contends, there also isn’t proof that it is harmless.

“Until a company can demonstrate the use of nanomaterials is safe, we’re asking companies either to not use them or to provide labels,” says Fugere. “It would make more sense to understand these materials before putting them in our food.”

As I understand it, Dunkin’ Donuts will be removing all titanium dioxide, nano-sized or other, from powdered sugar used in its products. It seems As You Sow’s promise to withdraw its July 2104 shareholder resolution is the main reason for Dunkin’ Donuts’ decision. While I was and am critical of Dunkin’ Donuts’ handling of the situation with As You Sow, I am somewhat distressed that the company seems to have acquiesced on the basis of research which is, at best, inconclusive.

Dr. Andrew Maynard, director of the University of Michigan Risk Science Centre, has written a substantive analysis of the current situation regarding nano titanium dioxide in a March 12, 2015 post on his 2020 Science blog (Note: Links have been removed),

Titanium dioxide (which isn’t the same thing as the metal titanium) is an inert, insoluble material that’s used as a whitener in everything from paper and paint to plastics. It’s the active ingredient in many mineral-based sunscreens. And as a pigment, is also used to make food products look more appealing.

Part of the appeal to food producers is that titanium dioxide is a pretty dull chemical. It doesn’t dissolve in water. It isn’t particularly reactive. It isn’t easily absorbed into the body from food. And it doesn’t seem to cause adverse health problems. It just seems to do what manufacturers want it to do – make food look better. It’s what makes the powdered sugar coating on donuts appear so dense and snow white. Titanium dioxide gives it a boost.

And you’ve probably been consuming it for years without knowing. In the US, the Food and Drug Administration allows food products to contain up to 1% food-grade titanium dioxide without the need to include it on the ingredient label. Help yourself to a slice of bread, a bar of chocolate, a spoonful of mayonnaise or a donut, and chances are you’ll be eating a small amount of the substance.

…

Andrew goes on to describe the concerns that groups such as You As Sow have (Note: Links have been removed),

For some years now, researchers have recognized that some powders become more toxic the smaller the individual particles are, and titanium dioxide is no exception. Pigment grade titanium dioxide – the stuff typically used in consumer products and food – contains particles around 200 nanometers in diameter, or around one five hundredth the width of a human hair. Inhale large quantities of these titanium dioxide particles (I’m thinking “can’t see your hand in front of your face” quantities), and your lungs would begin to feel it.

If the particles are smaller though, it takes much less material to cause the same effect.

But you’d still need to inhale very large quantities of the material for it to be harmful. And while eating a powdered donut can certainly be messy, it’s highly unlikely that you’re going to end up stuck in a cloud of titanium dioxide-tinted powdered sugar coating!

… Depending on what they are made of and what shape they are, research has shown that some nanoparticles are capable of getting to parts of the body that are inaccessible to larger particles. And some particles are more chemically reactive because of their small size. Some may cause unexpected harm simply because they are small enough to throw a nano-wrench into the nano-workings of your cells.

This body of research is why organizations like As You Sow have been advocating caution in using nanoparticles in products without appropriate testing – especially in food. But the science about nanoparticles isn’t as straightforward as it seems.

As Andrew notes,

First of all, particles of the same size but made of different materials can behave in radically different ways. Assuming one type of nanoparticle is potentially harmful because of what another type does is the equivalent of avoiding apples because you’re allergic to oysters.

He describes some of the research on nano titanium dioxide (Note: Links have been removed),

… In 2004 the European Food Safety Agency carried out a comprehensive safety review of the material. After considering the available evidence on the same materials that are currently being used in products like Dunkin’ Donuts, the review panel concluded that there no evidence for safety concerns.

Most research on titanium dioxide nanoparticles has been carried out on ones that are inhaled, not ones we eat. Yet nanoparticles in the gut are a very different proposition to those that are breathed in.

Studies into the impacts of ingested nanoparticles are still in their infancy, and more research is definitely needed. Early indications are that the gastrointestinal tract is pretty good at handling small quantities of these fine particles. This stands to reason given the naturally occurring nanoparticles we inadvertently eat every day, from charred foods and soil residue on veggies and salad, to more esoteric products such as clay-baked potatoes. There’s even evidence that nanoparticles occur naturally inside the gastrointestinal tract.

He also probes the issue’s, nanoparticles, be they titanium dioxide or otherwise, and toxicity, complexity (Note: Links have been removed),

There’s a small possibility that we haven’t been looking in the right places when it comes to possible health issues. Maybe – just maybe – there could be long term health problems from this seemingly ubiquitous diet of small, insoluble particles that we just haven’t spotted yet. It’s the sort of question that scientists love to ask, because it opens up new avenues of research. It doesn’t mean that there is an issue, just that there is sufficient wiggle room in what we don’t know to ask interesting questions.

… While there is no evidence of a causal association between titanium dioxide in food and ill health, some studies – but not all by any means – suggest that large quantities of titanium dioxide nanoparticles can cause harm if they get to specific parts of the body.

For instance, there are a growing number of published studies that indicate nanometer sized titanium dioxide particles may cause DNA damage at high concentrations if it can get into cells. But while these studies demonstrate the potential for harm to occur, they lack information on how much material is needed, and under what conditions, for significant harm. And they tend to be associated with much larger quantities of material than anyone is likely to be ingesting on a regular basis.

They are also counterbalanced by studies that show no effects, indicating that there is still considerable uncertainty over the toxicity or otherwise of the material. It’s as if we’ve just discovered that paper can cause cuts, but we’re not sure yet whether this is a minor inconvenience or potentially life threatening. In the case of nanoscale titanium dioxide, it’s the classic case of “more research is needed.”

Dexter Johnson in a March 11, 2015 post on his Nanoclast blog also weighs in on the discussion. He provides a very neat summary of the issues along with these observations (Note Links have been removed),

With decades of TiO2 being in our food supply and no reports of toxic reactions, it would seem that the threshold for proof is extremely high, especially when you combine the term “nano” with “asbestos”.

As You Sow makes sure to point out that asbestos is a nanoparticle. While the average diameter of an asbestos fiber is around 20 to 90 nm, their lengths varied between 200 nm and 200 micrometers.

The toxic aspect of asbestos was not its diameter, but its length. …

In addition to his summary Dexter highlights As You Sows attempt to link titanium dioxide nanoparticles to asbestos. I suggest reading his post for an informed description of what made asbestos so toxic (here) and why the linkage seems specious at this time.

When technology is used before ensuring that it is safe for humans and the environment, and before regulatory standards exist, companies can be exposed to significant financial, legal, and reputational risk. The limited studies that exist on nanomaterials, including nanoscale titanium dioxide*, have indicated that ingestion of these particles may pose health hazards.

The inaction of regulators does not protect companies, especially when the regulators themselves warn of the dangers of nanoparticles’ largely unknown risks. Draft guidance issued by the U.S. Food and Drug Administration raises questions about the safety of nanoparticles and demonstrates the general lack of knowledge about the technology and its effects. (1)

Asbestos litigation is a good example of the risks that can arise from using an emerging technology before it is proven safe. Use of asbestos (a nanomaterial) has created the longest, most expensive mass tort in national history with total U.S. costs now standing at over $250 billion. (2) If companies been asked to investigate and minimize or avoid risks prior to adopting asbestos technology, a sad and expensive chapter in worker harm could have been avoided.

* Titanium dioxide is a common pigment and FDA-approved food additive. It is used as a whitener, a dispersant, and a thickener.

While I don’t particularly appreciate fear-mongering as a tactic, the strategy of targeting investors and their concerns, seems to have helped As You Sow win its way.

A March 10, 2015 news item on Nanowerk highlights some research into the removal of nanoscale titanium dioxide particles from water supplies (Note: A link has been removed),

The increased use of engineered nanoparticles (ENMs) in commercial and industrial applications is raising concern over the environmental and health effects of nanoparticles released into the water supply. A timely study that analyzes the ability of typical water pretreatment methods to remove titanium dioxide, the most commonly used ENM, is published in Environmental Engineering Science (“Titanium Dioxide Nanoparticle Removal in Primary Prefiltration Stages of Water Treatment: Role of Coating, Natural Organic Matter, Source Water, and Solution Chemistry”). The article is available free on the Environmental Engineering Science website until April 10, 2015.

Nichola Kinsinger, Ryan Honda, Valerie Keene, and Sharon Walker, University of California, Riverside, suggest that current methods of water prefiltration treatment cannot adequately remove titanium dioxide ENMs. They describe the results of scaled-down tests to evaluate the effectiveness of three traditional methods—coagulation, flocculation, and sedimentation—in the article “Titanium Dioxide Nanoparticle Removal in Primary Prefiltration Stages of Water Treatment: Role of Coating, Natural Organic Matter, Source Water, and Solution Chemistry.”

“As nanoscience and engineering allow us to develop new exciting products, we must be ever mindful of associated consequences of these advances,” says Domenico Grasso, PhD, PE, DEE, Editor-in-Chief of Environmental Engineering Science and Provost, University of Delaware. “Professor Walker and her team have presented an excellent report raising concerns that some engineered nanomaterials may find their ways into our water supplies.”

“While further optimization of such treatment processes may allow for improved removal efficiencies, this study illustrates the challenges that we must be prepared to face with the emergence of new engineered nanomaterials,” says Sharon Walker, PhD, Professor of Chemical and Environmental Engineering, University of California, Riverside.

Interestingly Sharon Walker and Nichola Kinsinger recently co-authored a paper (mentioned in my March 9, 2015 post) about copper nanoparticles and water treatment which concluded this about copper nanoparticles in water supplies,

The researchers found that the copper nanoparticles, when studied outside the septic tank, impacted zebrafish embryo hatching rates at concentrations as low as 0.5 parts per million. However, when the copper nanoparticles were released into the replica septic tank, which included liquids that simulated human digested food and household wastewater, they were not bioavailable and didn’t impact hatching rates.

Taking these these two paper into account (and the many others I’ve read), there is no simple or universal answer to the question of whether or not ENPs or ENMs are going to pose environmental problems.

Tony Ryan, as an individual (and with Helen Storey), knows how to provoke interest in a topic many of us find tired, air pollution. This time, Ryan and Storey have developed a laundry detergent additive through their Catalytic Clothing venture (mentioned previously in a Feb. 24, 2012 posting and in a July 8, 2011 posting). From Adele Peters’ July 22, 2014 article for Fast Company (Note: A link has been removed),

Here’s another reason cities need more pedestrians: If someone is wearing clothes that happened to be washed in the right detergent, just their walking down the street can suck smog out of the surrounding air.

For the last few years, researchers at the Catalytic Clothing project have been testing a pollution-fighting laundry detergent that coats clothing in nano-sized particles of titanium dioxide. The additive traps smog and converts it into a harmless byproduct. It’s the same principle that has been used smog-eating buildings and roads, but clothing has the advantage of actually taking up more space.

Kasey Lum in a June 25, 2014 article for Ecouterre describes the product as a “laundry additive [which] could turn clothing in mobile air purifiers,”

CatClo piggybacks the regular laundering process to deposit nanoparticles of titanium dioxide onto the fibers of the clothing. Exposure to light excites electrons on the particles’ surface, creating free radicals that react with water to make hydrogen peroxide. This, in turn, “bleaches out” volatile organic compounds and nitrogen oxides in the atmosphere, according to Storey, rendering them harmless.

Lum referenced a May 23, 2014 article written by Helen Storey and Tony Ryan for the UK’s Guardian, newspaper which gives a history of their venture, Catalytic Clothing, and an update on their laundry additive (Note: Links have been removed),

It was through a weird and wonderful coincidence on BBC [British Broadcasting Corporation] Radio 4 that we met to discuss quantum mechanics and plastic packaging, resulting in the Wonderland Project, where we created disappearing gowns and bottles as a metaphor for a planet that is going the same way.

Spurred by this collaborative way of working, Wonderland led to Catalytic Clothing, a liquid laundry additive. The idea came out of conversations about how we could harness the surface of our clothing and the power of fashion to communicate complex scientific ideas – and so began the campaign for clean air.

(When I first wrote about Catalytic Clothing I was under the impression that it was an art/science venture focused on clothing as a means of cleaning the air. I was unaware they were working on a laundry additive.)

Getting back to Storey’s and Ryan’s article (Note: A link has been removed),

Catalytic Clothing (CatClo) uses existing technology in a radical new way. Photocatalytic surface treatments that break down airborne pollutants are widely applied to urban spaces, in concrete, on buildings and self-cleaning glass. The efficacy is greatly increased when applied to clothing – not only is there a large surface area, but there is also a temperature gradient creating a constant flux of air, and movement through walking creates our own micro-wind, so catalysing ourselves makes us the most effective air purifiers of them all.

CatClo contains nanoparticles of titania (TiO2) a thousand times finer than a human hair. [generally nanoscale is described as between 1/60,000 to 1/100,000 of a hair’s width] When clothes are laundered through the washing process, particles are deposited onto the fibres of the fabric. When the catalysed clothes are worn, light shines on the titanium particles and it excites the electrons on the particle surface. These electrons cause oxygen molecules to split creating free-radicals that then react with water to make hydrogen peroxide. This then bleaches out the volatile organic compounds and nitrogen oxides (NOx) that are polluting the atmosphere.

The whole process is sped up when people, wearing the clothes, are walking down the street. The collective power of everyone wearing clothes treated with CatClo is extraordinary. If the whole population of a city such as Sheffield was to launder their clothes at home with a product containing CatClo technology they would have the power to remove three tonnes per day of harmful NOx pollution.

So, if the technology exists to clear the air, why isn’t it available? From Storey’s and Ryan’s article,

Altruism, is a hard concept to sell to big business. We have approached and worked with some of the world’s largest producers of laundry products but even though the technology exists and could be relatively cheap to add to existing products, it’s proved to be a tough sell. The fact that by catalysing your clothes the clean air you create will be breathed in by the person behind you is not seen as marketable.

A more serious issue is that photocatalysts can’t tell the difference between a bad pollutant and a “good” one; for example, it treats perfume as just another volatile organic compound like pollution. This is an untenable threat to an entire industry and existing products owned by those best able to take CatClo to market.

We’ve recently travelled to China to see whether CatClo could work there. China is a place where perfume isn’t culturally valued, but the common good is, so a country with one of the biggest pollution problems on the planet, and a government that isn’t hidebound by business as usual, might be the best place to start.

In the midst of developing their laundry additive, Storey and Ryan produced a pop-up exhibition, A Field of Jeans (first mentioned here in an Oct. 13, 2011 posting which lists events for the 2011 London Science Festival), to raise public awareness and support (from the article),

During the research period, we realised that there were more jeans on the planet than people. Knowing this, we launched a pop-up exhibition, A Field of Jeans. The jeans we catalysed are all recycled and as it turns out, because of the special nature of cotton denim, are the most efficacious fabric of all to support the catalysts.

The public have been overwhelmingly supportive; once fears about the “chemicals”, “nanotech” or becoming dirt magnets were dispelled, we captured people’s imagination and proved that CatClo could eventually be as normal as fluoride in toothpaste with enormous potential to increase wellbeing and clean up our polluted cities.

New 2013/2014
Field of Jeans is at Thomas Tallis school from December 2nd 2013 until further notice. Jeans can be viewed from Kidbrooke Park Road, London SE3 outside the main school entrance. This will inspire a piece of work across the school called Catalytic Learning. More will be posted here soon.
Click here for imageshttp://www.thomastallis.co.uk/

Here’s an image from the Field of Jeans,

Image can be found here at: https://www.flickr.com/photos/helenstoreyfoundation/sets/72157638346745735/

I last featured Tony Ryan’s work here in a May 15, 2014 posting about a poem and a catalytic billboard at the University of Sheffield where Ryan is the Pro-Vice-Chancellor for Science.

Sandia National Laboratories (Sandia Labs) doesn’t ask directly but I think the call for partners is more than heavily implied. Let’s start with a June 17, 2014 news item on ScienceDaily,

Sandia National Laboratories has come up with an inexpensive way to synthesize titanium-dioxide nanoparticles and is seeking partners who can demonstrate the process at industrial scale for everything from solar cells to light-emitting diodes (LEDs).

Titanium-dioxide (TiO2) nanoparticles show great promise as fillers to tune the refractive index of anti-reflective coatings on signs and optical encapsulants for LEDs, solar cells and other optical devices. Optical encapsulants are coverings or coatings, usually made of silicone, that protect a device.

Industry has largely shunned TiO2 nanoparticles because they’ve been difficult and expensive to make, and current methods produce particles that are too large.

Sandia became interested in TiO2 for optical encapsulants because of its work on LED materials for solid-state lighting.

Current production methods for TiO2 often require high-temperature processing or costly surfactants — molecules that bind to something to make it soluble in another material, like dish soap does with fat.
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Those methods produce less-than-ideal nanoparticles that are very expensive, can vary widely in size and show significant particle clumping, called agglomeration.

Sandia’s technique, on the other hand, uses readily available, low-cost materials and results in nanoparticles that are small, roughly uniform in size and don’t clump.

“We wanted something that was low cost and scalable, and that made particles that were very small,” said researcher Todd Monson, who along with principal investigator Dale Huber patented the process in mid-2011 as “High-yield synthesis of brookite TiO2 nanoparticles.” [emphases mine]

Their (Monson and Huber) method produces nanoparticles roughly 5 nanometers in diameter, approximately 100 times smaller than the wavelength of visible light, so there’s little light scattering, Monson said.

“That’s the advantage of nanoparticles — not just nanoparticles, but small nanoparticles,” he said.

Scattering decreases the amount of light transmission. Less scattering also can help extract more light, in the case of an LED, or capture more light, in the case of a solar cell.

TiO2 can increase the refractive index of materials, such as silicone in lenses or optical encapsulants. Refractive index is the ability of material to bend light. Eyeglass lenses, for example, have a high refractive index.

Practical nanoparticles must be able to handle different surfactants so they’re soluble in a wide range of solvents. Different applications require different solvents for processing.

…

“If someone wants to use TiO2 nanoparticles in a range of different polymers and applications, it’s convenient to have your particles be suspension-stable in a wide range of solvents as well,” Monson said. “Some biological applications may require stability in aqueous-based solvents, so it could be very useful to have surfactants available that can make the particles stable in water.”

The researchers came up with their synthesis technique by pooling their backgrounds — Huber’s expertise in nanoparticle synthesis and polymer chemistry and Monson’s knowledge of materials physics. The work was done under a Laboratory Directed Research and Development project Huber began in 2005.

“The original project goals were to investigate the basic science of nanoparticle dispersions, but when this synthesis was developed near the end of the project, the commercial applications were obvious,” Huber said. The researchers subsequently refined the process to make particles easier to manufacture.

Existing synthesis methods for TiO2 particles were too costly and difficult to scale up production. In addition, chemical suppliers ship titanium-dioxide nanoparticles dried and without surfactants, so particles clump together and are impossible to break up. “Then you no longer have the properties you want,” Monson said.

The researchers tried various types of alcohol as an inexpensive solvent to see if they could get a common titanium source, titanium isopropoxide, to react with water and alcohol.

The biggest challenge, Monson said, was figuring out how to control the reaction, since adding water to titanium isopropoxide most often results in a fast reaction that produces large chunks of TiO2, rather than nanoparticles. “So the trick was to control the reaction by controlling the addition of water to that reaction,” he said.

…

Some textbooks dismissed the titanium isopropoxide-water-alcohol method as a way of making TiO2 nanoparticles. Huber and Monson, however, persisted until they discovered how to add water very slowly by putting it into a dilute solution of alcohol. “As we tweaked the synthesis conditions, we were able to synthesize nanoparticles,” Monson said.

Whoever wrote the news release now makes the plea which isn’t quite a plea (Note: A link has been removed),

The next step is to demonstrate synthesis at an industrial scale, which will require a commercial partner. Monson, who presented the work at Sandia’s fall Science and Technology Showcase, said Sandia has received inquiries from companies interested in commercializing the technology.

“Here at Sandia we’re not set up to produce the particles on a commercial scale,” he said. “We want them to pick it up and run with it and start producing these on a wide enough scale to sell to the end user.”

Sandia would synthesize a small number of particles, then work with a partner company to form composites and evaluate them to see if they can be used as better encapsulants for LEDs, flexible high-index refraction composites for lenses or solar concentrators. “I think it can meet quite a few needs,” Monson said.

In my Sept. 25, 2013 posting I highlighted a then upcoming Guardian-hosted ‘nanotechnology and food’ panel discussion titled, Should we use nanotechnology to feed ourselves? The discussion has since taken place and resulted in a report (Oct. 22, 2013 ?) written by Penny Sarchet and posted on the Guardian website space devoted to Nanofutures, a specially commissioned section which is sponsored by NanOpinion, an EU-funded (European Union) project (from the posted report),

Ordinarily, the chair or the moderator is separated out from the list of panelists. I’m not sure if it’s a formatting issue or if Ian Illuminato’s name is being given special significance; this is never made clear in the report. On a related note, here’s a question for you, which one of these panelist’s employers is different from the others?

Illuminato’s employer, Friends of the Earth (FoE), describes itself this way (from the About Us page) Note: A link has been removed,

Friends of the Earth strives for a more healthy and just world. We understand that the challenges facing our planet call for more than half measures, so we push for the reforms that are needed, not merely the ones that are politically easy. Sometimes, this involves speaking uncomfortable truths to power and demanding more than people think is possible. It’s hard work. But the pressures facing our planet and its people are too important for us to compromise.

We are members of Friends of the Earth International, a global network representing more than two million activists in 74 different countries. …

Groves’s employer, Leatherhead Food Research, describes itself this way (from the About Us page),

Founded in 1919, Leatherhead Food Research has been a trusted partner to the food industry for nearly a century, offering an unparalleled breadth and depth of experience to help the food industry innovate and evolve.

Our Members and clients represent a who’s who of the global food and beverage market – ranging from large multi-nationals to SMEs, and including ingredient suppliers, manufacturers, retailers and foodservice businesses. Leatherhead Food Research has a unique Membership that includes over 1500 food and drinks companies worldwide.

Leatherhead Food Research offers services including market intelligence, food research and analysis, food legislation, business and technical information and training. Additionally, we can deliver bespoke consulting and research services to both Members and non-Member organisations.

Jones’s employer, Food and Drink Federation, describes itself this way (from the Who we are page),

The Food and Drink Federation is the voice of the UK food and drink industry, the largest manufacturing sector in the country.

Our sector directly employs up to 400,000 people, and as many as 1.2 million in ancillary services; it accounts for 16% of the UK’s total manufacturing sector by value; and it is an invaluable partner to British agriculture, buying two thirds of what farmers produce. Our membership comprises manufacturers of all sizes as well as trade associations dealing with specific sectors of the industry.

Formatting aside, it’s clear the organizers were trying to represent more than one position with the industry types being ‘pro’ nanotechnology in food and the lone civil society rep representing the ‘con’ position, in a moderate fashion (i”ll get back to ‘moderate’ in a moment).

Here are some excerpts from the report,

A recent Guardian seminar [Should we use nanotechnology to feed ourselves?], sponsored by the European Commission, met to debate how we will continue to feed the world, and the panellists – Terry Jones, Kathy Groves and Ian Illuminato, chaired by Alok Jha – considered how important nanotechnology is likely to be in this task. Their opinions were listened to by members of an invited public audience, who were also able to put questions to the panel.

…

The current use of nanotechnology in the food industry is still in its early stages and generally builds upon longstanding processes and practices in food production. Jones, however, says it is clear that nanotechnology might provide solutions to a range of industry problems.

“You could see nanotechnology used in the cultivation, production, processing or packaging of food,” he said. “It could be used to develop new food products or, indeed, improve existing ones.”

As well as reducing water use and contamination in food processing, Jones believes nanotechnology could help make food healthier.

…

These ideas sound ambitious and all-encompassing, but, in reality, the current use of nanotechnology in food production is limited. An often-cited contemporary example is nanosalt, smaller grains of salt that provide better coverage of a plate of chips while reducing the overall amount of salt used. So far, however, it has been slow to catch on.

…

This reluctance to accept nanotechnological tinkering in the food industry is shared by Illuminato, of campaign group Friends of the Earth. He believes that many questions about nanotechnology remain to be answered and, until they have been, it is sensible to be cautious.

“Nanoparticles can be more chemically reactive, they can have greater access to our bodies than larger particles, and when they become more bio-available there’s a question of whether that also introduces new toxicity risks,” said Illuminato.

He is concerned that, because of their extremely small size, nanoparticles might interfere with DNA or be able to cross the human placenta and blood-brain barriers. “I’m not somebody who thinks technology is malicious – I think it’s humans that put that on to the technology,” said Illuminato. [emphasis mine] “It’s how we manage these things that’s going to be important.”

There’s no indication as to what the 25 audience members thought about the session although Hilary Sutcliffe of Matter was quoted,

Audience member Hilary Sutcliffe, director of the Matter think tank on responsible innovation, was keen to emphasise the limits of nanotechnology in food. “If we’re really lucky, we might get nanosalt and a couple of nano-encapsulated vitamins that go in products,” she told the panel, describing her disappointment in the progress of nanotechnology in food to date.

Sutcliffe explained that these limited applications are expensive and not that useful: manufacturers would rather just reduce salt content than pay for nanosalt, and vitamins and flavourings do not need to be nano-encapsulated because they can be added to foods at the microscale, rather than at the nano-level, which is one thousand times smaller.

She also suggested that, so far, the possible uses of nanotechnology have only been in Western diets and that people should be realistic about its use for tackling the impending global food crisis. “Nothing about nanotechnology is in relation to anything except Western, expensive foods that are slightly gratuitous and not particularly necessary,” she said, before adding that it is not currently helping to feed the world. “If you are going to talk about feeding the world, be brave, take on GM, let’s have that discussion.”

All in all, it seems the panel discussion was an interesting exercise although I’m not sure what it was in aid of. Perhaps that will become more clear with the passage of time.

Finally, getting back to Illuminato and the FoE’s moderate position. This signals a distinct change in tone since the days when FoE engaged in a relentless campaign against nanosunscreens and since the debacle in Australia (described in my Feb. 5, 2012 posting). While this news release head suggests the ‘old’ FoE campaign, the text doesn’t distort the research, as far as I know, (from the FoE March 5, 2013 news release),

Today, Friends of the Earth U.S. and Australia revealed new testing results from the Australian Government’s National Measurement Institute, which found that many popular sunscreen and cosmetic products are using a potentially hazardous form of a common ingredient — anatase titanium dioxide. Six of the eight products tested, including well-known brands such as Nivea (Beiersdorf AG (BEIG.DE)), L’Oreal SA (OREP.PA), and CoverGirl (Procter & Gamble Co (NYSE:PG)), were found to contain this ingredient.

“The product we are most concerned about is Nivea Sun ‘Kids Swim and Play’ sunscreen, since independent analysis of the test results by Uniquest found that more than 90 percent of the particles extracted from the product were nanoparticles. (note 1) Due to their large relative surface area, nanoparticles of anatase titanium dioxide are much more reactive than larger particles of the chemical. Protecting our skin from the sun is no joke, and sunscreens are an important part of staying safe from harmful UV rays. On the other hand, some sunscreens may not be as effective and safe as we think,” said Ian Illuminato, health and environment campaigner at Friends of the Earth U.S.

Some skin cancers are linked to UV-induced free radical damage to the skin, which is why wearing sunscreens with strong broad-spectrum UVA/UVB protection is recommended by medical authorities. However, recent studies have shown that the anatase form of titanium dioxide (and in particular nano-scale anatase titanium dioxide) can increase the formation of free radicals when exposed to sunlight and water and a number of scientists have questioned the safety of their use in sunscreens and other skin products. Anatase is an aggressive free radical producer compared to rutile, another less reactive form of titanium dioxide used in sunscreens, cosmetics and other products.

In 2008, a peer reviewed study found that nano anatase titanium dioxide in sunscreen was reacting with sunlight and breaking down the coating on steel roofing in a matter of weeks. This study was prompted by reports that coatings on roofs were breaking down in places where workers had inadvertently transferred sunscreen to roofs via skin contact. Researchers from the 2008 study found that this sunscreen ingredient increased the normal rate of sun damage to the roofs by 100 times. (note 2) The study raised serious concerns about the impact these ingredients may be having on our skin. In 2010, Italian scientists warned that anatase titanium dioxide is “capable of destroying virtually any organic matter.” (note 3)

I’ve highlighted the carefully worded injunction to use sunscreens as they are important to your safety. As I recall, prior to the debacle, FoE didn’t make the effort.

As for the research about anatase and rutile forms of nano titanium dioxide mentioned in in FoE’s March 2013 news release, I have only recently noted this in my blog (Oct. 3,2013 posting). Somehow I missed the research in Australia.

The American Chemical Society (ACS) features some research into nanoscreens and the anatase form of titanium dioxide in a Sept. 25, 2013 news release,,

Using a particular type of titanium dioxide — a common ingredient in cosmetics, food products, toothpaste and sunscreen — could reduce the potential health risks associated with the widely used compound. The report on the substance, produced by the millions of tons every year for the global market, appears in the ACS journal Chemical Research in Toxicology.
Francesco Turci and colleagues explain that titanium dioxide (TiO2) is generally considered a safe ingredient in commercially available skin products because it doesn’t penetrate healthy skin. But there’s a catch. Research has shown that TiO2 can cause potentially toxic effects when exposed to ultraviolet light, which is in the sun’s rays and is the same kind of light that the compound is supposed to offer protection against. To design a safer TiO2 for human use, the researchers set out to test different forms of the compound, each with its own architecture.

They tested titanium dioxide powders on pig skin (which often substitutes for human skin in these kinds of tests) with indoor lighting, which has very little ultraviolet light in it. They discovered that one of the two most commonly used crystalline forms of TiO2, called rutile, easily washes off and has little effect on skin. Anatase, the other commonly used form, however, was difficult to wash off and damaged the outermost layer of skin — even in low ultraviolet light. It appears to do so via “free radicals,” which are associated with skin aging. “The present findings strongly encourage the use of the less reactive, negatively charged rutile to produce safer TiO2-based cosmetic and pharmaceutical products,” the researchers conclude.

It should be noted that the researchers used pig skin, i.e., the skin was not on a pig and, therefore, not part of a living organism with its various biological systems coming into play. As well, the testing was done indoors not under direct sunlight which is the condition under which most of us use sunscreen. This research points to problems with using anatase nanoscale titanium dioxide in sunscreens but it doesn’t provide unequivocal proof.

The Danish Environmental Protection Agency report (this Oct. 3, 2013 posting of mine) on the state of the art of research into nanomateial dermal absorption does refer to research in this area, although it does not include Turci’s work (Note: The numbers n the excerpted text are reference numbers for the bibliography)),

When looking at bulk composition and the level of dermal penetration noted in studies using a specific material type, there appears to be very little pattern between bulk composition and penetration depth. Taking for example TiO2 as one of the most widely studied nanoparticles, we see reports of penetration no further than the SC [subcutaneous skin layer] 78, 86, 91 but also several studies suggesting deeper penetration (basal cell layer) and even penetration into the dermis 63, 84 although this is often reported as being a very small fraction/infrequent. Another compositional issue in relation to nanoparticles and in particular TiO2 is the crystalline structure. TiO2 is often used in either its anatase or rutile form or as mixture of both. Within the literature, there are studies using both the anatase form 86, 94, the rutile form 91, 114 or a mixture 84, 114 although we were unable to find any studies which appear to systematically evaluate the role of crystal form in TiO2 absorption into the skin. [emphasis mine] (p. 44 of this report: Dermal Absorption of Nanomaterials Part of the ”Better control of nano” initiative 2012 – 2015 Environmental Project No. 1504, 2013).

There’s a Sept. 27, 2013 news item about the Czech Republic’s latest technology mission to China on the Nanowerk website,

This week [Sept. 23 – 27, 2013], the representatives of Czech nanotechnology firms, two famous technical universities and CzechInvest took part in a technology mission to China, where they met Chinese counterparts and discussed the further strengthening of cooperation in the field of nanotechnology. This technology mission to China, together with activities of some Czech nanotechnology companies, which have also been extensively supported by the Czech embassy in Beijing in recent months, has brought new opportunities for investment and the further collaboration of highly innovative technologies originated in the Czech Republic.

“The Czech Republic is a world leader in the field of nanotechnology, which has an impact on numerous industrial sectors and places major demands on research. Czech nanotechnology firms are highly respected on the Chinese market,” says Marian Piecha, CEO of CzechInvest.

Representatives of CzechInvest, the Technical University of Liberec, Brno University of Technology and the Czech nanotechnology firms NAFIGATE Corporation, Elmarco, ACT Nami and Noen are taking part in CHINanoForum 2013, which is being held from 24 to 27 September in Jiangsu province. Within the forum’s accompanying programme, CzechInvest and NAFIGATE Corporation conducted a seminar title Nanosolutions for Green Economy – Investment Opportunity in China on 24 September. On 27 September the Czech delegates and their Chinese counterparts will be at the Czech embassy in Beijing to discuss the topic of using nanotechnologies in water treatment, among other things.

“China offers tremendous space for introducing new high-tech products to the market,” says Ladislav Mareš, chairman of the board of directors of NAFIGATE Corporation. “This technology mission therefore has major significance for supporting Czech exports to the Chinese market. Presentation of the potential of Czech nanotechnologies is also a signal for Chinese investors.”

According to the news release, a memorandum of understanding will be signed,

Technological cooperation between the two countries will also be supported by the signing of a Memorandum of Understanding between the Technology Agency of the Czech Republic and the Suzhou Industrial Park Administrative Committee. The signing of the memorandum, which will facilitate cooperation between Czech and Chinese firms with a high technological profile, will be attended by representatives of CzechInvest and His Excellency Libor Sečka, the Czech ambassador in China.

Earlier this years, in June 2013, Nafigate signed a letter of intent with its Chinese partner, Guodian Technology & Environment Group Corporation Limited, regarding the development of a green nanotechnology centre. From a June 21, 2013 news release on PR newswire,

In the last few days, Czech nanotechnology pioneers have been presenting possible ways of utilizing Czech nanotechnology with specific examples taken from the Clean Air Nanosolution and Clean Water Nanosolution projects to representatives of the most significant Chinese companies at the Embassy of the Czech Republic in Beijing. “There is a lot of interest in the new technology because it solves fundamental problems in air and water cleaning. At the same time the Czech Republic is the world leader in the field of nanofibers and has much to offer China, from cooperation in research and development to putting specific innovative approaches into practice. Cooperation in this field could become an important new branch of mutual trade and scientific and technological exchanges and bring qualitative changes in the life of Chinese society,” said H. E. Mr. Libor Secka, Ambassador of the Czech Republic to the People’s Republic of China.

The signing of the Letter of Intent between NAFIGATE China (a subsidiary of the Czech company NAFIGATE Corporation JSC) and their Chinese partner Guodian Technology & Environment Group Corporation Limited (a subsidiary of one of the most prominent Chinese energy companies) is a significant milestone in Czech-Chinese cooperation in nanotechnology sector. Since January 2013 both companies have been preparing the foundation of the NANODEC (Nanofiber Development Center) project for the development of final applications for water and air cleaning.

The establishment of the center will be a major breakthrough with a global impact in the field of nanofiber applications. The aim of this initiative is to build a center of excellence which will utilize the best available worldwide know-how, the technological and infrastructural potential of one of the most significant Chinese companies and the potential of the market for new low carbon and green technologies. The Letter of Intent specifies the steps required to open the center according to the schedule in the last quarter of 2013.

For those interested in the overall nanotechnology scene in the Czech Republic, I found a 2012 article in the New York Times and a paper (2009?) written for the National Information Centre For European Research (NICER) and located on the Organization of Economic Cooperation and Development.

Industries based on nanotechnology are a rapidly growing niche in the economy of the Czech Republic, which, although small, is widely respected for its technical prowess. In February, the country had its own pavilion at the International Nanotechnology Trade Fair, Nanotech 2012, in Tokyo. Ten Czech companies took part.

One was Advanced Materials-JTJ, which produces photocatalytic coating materials incorporating titanium dioxide nanoparticles, known as FN coatings. The semi-transparent, odorless coatings have the unusual property of purifying the air around them — removing viruses, bacteria, toxins, cigarette smoke and more through a light-activated catalytic process.

…

Over the course of a year, “one square meter of FN-painted facade will clean and decontaminate over three million cubic meters of air,” or 106 million cubic feet, removing several kilograms of pollution, Mr. Prochazka [Jan Prochazka, Advanced Materials-JTJ’s chief executive] said.

As well as cleaning the air, the coating protects the painted surfaces from mold, fungus and the slow accumulation of dirt deposits that cause erosion and discoloring, he said.

The process, activated by ultraviolet light — that is, sunshine — is both environmentally friendly and cost-effective.

“For many people nano is a question mark, but really, everything is nano, except for gravel, sand and a few other materials,” Mr. Prochazka said in an interview in Prague. “Take a cup of water; you can’t imagine how many nanoparticles are inside.”